In general, for manufacturing a semiconductor element, predetermined processing is performed while a reactive gas is introduced into a reaction chamber in processing equipment, for example, a film formation system by CVD (chemical vapor deposition), an oxidation/diffusion system for processing the surface of a semiconductor wafer, a dry etching system for forming a wiring pattern in a thin film, or the like. For example, in forming a film of poly-Si, SiO2, Si2N4, or the like, a reactive gas, such as SiH4, Si2H6, SiH2, Cl2, NH3, PH3, N2O, TEOS, or the like is introduced into the reaction chamber to form a corresponding film on a semiconductor substrate by thermal treatment.
The reactive gases used in the processing by these systems have low utilization efficiency of several percentages, and almost all the reactive gases are discharged as unreacted gases. When an exhaust gas including such an unreacted gas passes through an exhaust passage, the unreacted gas coagulates due to temperature lowering of the exhaust gas to precipitate a solid material (for example, NH4Cl and AlCl3) made of a reaction product, a liquefied material from a film formation gas, and the like on the inner walls of the pipes and the like. When the pressure in the reaction chamber is changed, for example, from a reduced pressure atmosphere to an air pressure atmosphere, the solid material precipitated in the exhaust passage flies back (backflow) into the reaction chamber to adhere to a semiconductor wafer, thereby leading to lowering of yield of the semiconductor element.
In view of the foregoing, in such an exhaust system, an exhaust pressure controller for reducing overpressure by evacuation is provided between the reaction chamber and a vacuum pump. With the exhaust pressure controller, a residual film formation component is diluted by introducing an inert gas, and overpressure is reduced by evacuation. In an exhaust pressure controller of some types, a plurality (for example, three to five) piping joints are connected to an exhaust pipe thereof for diluting the residual film formation component by introducing the inert gas and the like in addition to pressure adjustment by gas introduction/discharge. The piping joints are connected to an inert gas supply apparatus composed of an introduction pipe, a flow controller, a regulator, a chemical cylinder, and the like, a vacuum pump, and the like (see Patent Document 1, for example). Patent Document 1: Japanese Patent Application Laid Open Publication No. 5-17287